Project 3: Project Summary/Abstract Exposure of people to single chemicals or mixtures at Superfund sites has unquestionably occurred. The unanswered question addressed here is whether those exposures can be associated with genetic risk, which would provide biological plausibility to the argument that the chemicals in the environment have affected human health and welfare. The compounds chosen for investigation were inspired by engagement efforts in several local communities containing Superfund sites. Carcinogenic N-nitrosamines (e.g., N-nitrosodimethylamine or NDMA) and polycyclic aromatic hydrocarbons (PAHs; e.g., benzo[a]pyrene (B(a)P)) are abundant at one or more of the sites in our catchment area. These agents have not been studied as mutagens at the level of detail proposed here, and they certainly have not been subjected to the combined scrutiny of this Project, along with Project 4 (DNA damage and gene-environment interactions) and Project 5 (signal transduction disruption). The technology of Project 3 has three components: (a) a genetically engineered mouse that responds to environmental toxicants in a manner that predicts end-stage cancers; (b) a newly developed high-fidelity DNA sequencing procedure that provides unprecedentedly high-resolution mutational spectra (HRMS); and (c) a novel computational module that quantitatively compares HRMS from our mouse model with the rapidly expanding data set of The Cancer Genome Atlas Project (TCGA) and other tumor sequencing efforts. In preliminary work, the technology was tested using a natural liver carcinogen. The results convincingly show that our murine HRMS as early as 10 weeks after toxin administration are nearly identical to computationally extracted mutational patterns from human liver cancer (these HRMS are referred to as ?exposure spectra,? because tumors do not appear in our mouse model for over a year); this short time frame enables our proposed mechanistically detailed investigations of the role of gene-environment interactions as a contributor to cancer burden. The first Specific Aim examines the ?exposure mutational spectra? of NDMA and B(a)P as individual compounds and as mixtures; later it examines other compounds identified by Projects 1 and 2. The second Aim longitudinally tracks mutational spectra up to the development of tumors. It is expected that mutagenic processes independent of the initiating agent will superimpose their spectra on the early ?exposure spectrum.? From both Aims, informatics techniques will establish the extent of quantitative cosine similarity of the murine spectra with human tumor spectra mined from TCGA. The third Aim will probe gene-environment interactions. In collaboration with Project 4, the role of specific DNA damage response processes as molders of our HRMS will be evaluated. We also shall perturb the cellular environment of target tissues in the mouse by using chemo-prevention agents (e.g., Nrf2 inducers) that will help to define susceptibility factors that may be in play in human populations; these studies also provide intervention insight to modulate risk via lifestyle modification.